The probe collected "significant evidence of systemic and serious sexual and physical abuse of children" at the care homes, police said in a report.

The alleged victims, mostly men, were from seven to 19 years old when they say they were targeted between 1965 and 1992. The alleged offences ranged from verbal abuse to indecent assaults and rape.

"Many (of those interviewed) have provided graphic accounts of abuse, in some cases of very serious criminality," Detective Ian Mulcahey said.

The number of care homes was larger and the timeline involved was longer than previously thought.

The new investigation, known as Operation Pallial, was set up in November after a BBC report alleged that a previous inquiry failed to uncover the full extent of the abuse against children in the homes. The earlier inquiry, which concluded in 2000, settled dozens of claims on behalf of the victims.

Since Operation Pallial was launched, police said 140 complainants have come forward to name 84 individuals - 75 male, nine female - as being responsible for offences. One person has been detained in the new investigation.

Detectives said the inquiry was continuing and urged anyone with information to come forward.